The high-frequency MEMS element having variable capacity has a smaller signal loss and higher linearity than the conventional semiconductor element. It is therefore expected that the high-frequency MEMS element should be incorporated in next-generation wireless systems. In any wireless system of this type, so-called “hot switching” should be performed to switch the elements while high-frequency signals are passing through the elements.
In the hot switching performed in the MEMS element, the self-actuation and self-holding of the MEMS element become problems. To avoid the self-actuation, it suffices to set the pull-in voltage higher than the DC bias made effective by the high-frequency signal. That is, the self-actuation can be prevented in the MEMS device of the ordinary design. By contrast, to avoid the self-holding, the pull-out voltage need be higher than the DC bias made effective by the high-frequency signal. Inevitably, it is difficult to prevent the self-holding in the MEMS of the ordinary design.